This invention relates to methods and apparatus for crushing various materials. The invention is especially useful for reducing ore, rock, stone, coal, and the like. In mining or extraction, random size pieces of mineral material are produced, some too large to be carried out of the mine or quarry on conveyor belts of practical and economical width. Bucket or skiff conveyors have been tried, but have been expensive to build, operate and maintain. Thus, motor trucks have been used to carry uncrushed minerals from the bottom of mines or quarries to a distant or upper surface for crushing.
For various reasons, including perhaps the desire to provide reversible hammer rotation and design symmetry, the massive crushers most commonly used heretofore in the crushing of large chunks of heavy minerals have included a top inlet and bottom outlet. Positioning a conveyor belt below such a crusher to receive crushed material from the outlet involves elevating the crusher above ground on heavy supporting framework, or constructing a trench beneath it. This can raise the inlet to a difficult or prohibitive height for conventional mobile loaders or loading equipment, and/or makes the crusher considerably less mobile or less stable and more expensive to install.
In principle, mineral extraction costs can be reduced by crushing the large chunks to a convenient size in the quarry or at the mine face, and then carrying them to the surface by belt conveyors of practical size and width. However, under many circumstances, the above-described problems and the size and expense of available mobile crushers frustrate the use of this money-saving procedure.